To maximize HIV treatment as prevention efforts in San Francisco, we propose a three-year study that uses geospatial methods to map and analyze the distribution of HIV treatment outcomes at the neighborhood level. Since the publication of the HPTN 052 clinical trial findings in 2011, global HIV prevention efforts have heralded the use of early antiretroviral therapy (ART) as a key strategy to disrupt transmission events and end the HIV/AIDS epidemic in subsequent generations. A growing body of research is focused on the identification of interventions at the individual level that improve engagement in HIV care and reduce community viral load. However, few studies have investigated the neighborhood as a unit of analysis to determine characteristics and resources that facilitate entry into HIV treatment. Attention to the neighborhoods in which HIV positive individuals live, including availability of health care, housing, and public transportation services, is necessary to maximize the use of HIV treatment as prevention of new infections. Geospatial methods offer an innovative and underutilized approach to studying these issues. Aim 1. To examine spatial relationships between neighborhood characteristics and HIV treatment outcomes in San Francisco through the use of geographic information systems (GIS) software. Aim 2. To identify locations of resources which facilitate engagement in HIV treatment by utilizing methods of public participatory GIS (PPGIS) with HIV positive individuals. Aim 3. To create an online mapping platform for the dissemination of thematic maps showing gaps in HIV treatment outcomes and resources using data collected in Aims 1 and 2. We will achieve these aims through a mixed-methods study that is guided by Gardner's model of six stages of engagement in HIV care: 1) awareness of serostatus, 2) linkage to care, 3) retention in care, 4) access to ART, 5) adherence to ART, and 6) suppression of viral load. For Aim 1, data will be collected from secondary sources (SFDPH AIDS Office and the US Census), mapped using GIS software, and analyzed using spatial statistics. This information will help us identify gaps in engagement in care at the neighborhood level and determine predictors of optimal and suboptimal treatment outcomes. For Aim 2, we will conduct PPGIS focus groups with HIV positive individuals in selected neighborhoods. This information will help us identify HIV treatment-related resources at each stage of engagement in care. For Aim 3 we will create an online mapping platform to facilitate the dissemination of maps and findings to SFDPH, neighborhood health clinics, and HIV focused community based organizations. The methods and maps we develop through this study will facilitate the use of spatially-targeted programmatic and policy efforts to reduce community viral load by identifying gaps in treatment at the neighborhood level. The study is led by a new Early Stage Investigator (PI Dr. Alexis Martinez) and will support the goals of the R15 mechanism by providing a rich environment for students at a state university to learn about all aspects of the research process from an interdisciplinary team of investigators with a successful history of collaboration in both teaching and research institutions.